California Agriculture

The accurate determination of pubertal status in yearling beef heifers, possibly combined with the use of exogenous progesterone, allows females to produce the maximum number of calves over their lifetimes. This study aimed to determine the reliability of a reproductive tract scoring (RTS) system that combines manual palpation with ultrasound as a measure of pubertal status, and whether the treatment of heifers with progesterone-containing vaginal inserts — followed by breeding on the second estrus after removal of the insert — could result in increased conception rates compared to untreated heifers. Over 2 years, we found that RTS predicted pubertal status reasonably accurately. Progesterone-treated heifers were more likely to exhibit estrus than control heifers, but their overall breeding efficiency was not affected by progesterone treatment. Inadequate nutrition associated with increased pasture stocking density during both breeding seasons likely had a negative effect on the results of our study.